1. Field of the Invention
The present invention relates to a variable delay line of a lumped constant type composed of a combination of an inductance element and plural capacitors, and more particularly to a subminiature variable delay line suitable for use with the digital circuits of a computer, etc., which enables the changeover of the delay time in precise intervals.
2. Description of the Prior Art
Hitherto, lumped constant and distributed constant variable delay lines have been available. A conventional delay line of the lumped constant type composed of a combination of plural coil units and capacitors connected so as to switchably connect a coil unit in order to vary the delay time has been publicly known.
However, such variable delay lines are liable to be large in size because the coil unit is switchably connected in order to vary the delay time. Furthermore the delay time may be varied only within the range of a simple multiplier td where the delay time of the coil unit is given by td. As a result, it is impossible to change the delay time in precise intervals, and accordingly an optimum adjustment of the delay time becomes difficult when the delay line is incorporated into an electronic apparatus such as a computer.
On the other hand, distributed constant variable delay lines are composed of a solenoid coil wound around a bobbin so as to interpose a delay due to the inter-electrode capacitance distributed between said coil and ground. The delay time is varied by sliding a sliding member on the coil. However, such distributed constant variable delay lines have a defect in that the rise time thereof is slow, so that a fast delay time characteristic may not be obtained.
As mentioned above, there has not been realized a variable delay line with a fast rise time and ultra high speed which enables the changeover of the delay time in precise intervals.